Note: [esc]=[break] \=[clear]
This is using code for a javascript TRS-80 emulator from Peter Phillips at http://people.cs.ubc.ca/~pphillip/trs80.html.
To edit a line in basic type edit followed by the line number. After that space moves forward, backspace moves backward, enter exits the edit more, I goes to insert mode, and D deletes.
The cheat sheet below started with notes from Mike's Virtual Computer Museum at http://www3.nbnet.nb.ca/mclays/level2.html.
ABS(X)	 Returns the absolute value of x.
CLOAD	 Loads a program from cassette tape.
CLS	 Clears the video screen.
CONT	 Continues program execution after BREAK or STOP.
CSAVE	 Records (saves) a program on cassette tape.
DATA	 Holds data to be read by a READ statement in a program.
END	 Ends program execution.
FOR-NEXT-STEP	 Sets up a program loop.
GOSUB	 Sends the program to a specified subroutine.
GOTO	 Causes program execution to jump to a specified line number.
IF-THEN	 Tests for a condition, specifes next action if condition is true.
INPUT	 Allows keyboard entry of data during program execution.
INPUT#	 Inputs data from a cassette tape.
INT(X)	 Returns the integer value of x.
LET	 Assigns a value to a variable.
LIST	 Displays a program in memory on the video display.
MEM	 Returns the number of free bytes of memory.
NEW	 Clears program from memory.
ON	 Multi-way program branch, used with GOTO or GOSUB.
POINT	 Tests to see if a specifed graphics point is turned on or off.
PRINT	 Displays information on the video screen.
PRINTAT	 Allows printing at a specified video screen location.
PRINT#	 Records data on the cassette tape.
READ	 Reads information from DATA statement in a program.
REM	 Add a remark to the program.
RESET	 Turns off a specified graphics point on the video display.
RESTORE	 Causes the next READ statement to start over at the beginning of
         the DATA list.
RETURN	 Returns program to its original sequence after subroutine execution.
RND(1)	 Generates a random number >0 and <1.
RND(X)	 Generates a random number >1 and <=x.
RUN	 Starts program execution.
SET	 Lights up a specified graphics point on the video display.
STOP	 Stops program execution.
TAB	 Begins printing at a specified number of spaces from the left
         margin of the video screen.

ASC(A$)	 Returns ASCII code for first character of A$.
ATN(X)	 Returns the arctangent of X in radians.
AUTO	 Turns on the automatic line numbering feature. There was a
	 utility available under TRSDOS that allowed the renumbering
         of BASIC programs.
CDBL(X)	 Convert a value to double precision.
CHR$(X)	 Returns the ASCII character represented by the code x.
CINT(X)	 Converts value to Integer precision.
CLEAR	 Clears variables from memory.
CLEAR(X)	 Reserves string variable space.
CLOAD"FILE"	 Loads named file from cassette tape.
CLOAD?	 Verifies program saved to cassette tape by re-reading it and
         comparing it to the copy in memory.
COS(X)	 Returns the cosine, in radians.
CSAVE"FILE"	 Saves the program in memory to a cassette tape.
CSNG(X)	 Converts to single precision.
DEFDBL	 Defines specified variables as double precision.
DEFINT	 Defines specified variables as integer precision.
DEFSNG	 Defines specified variables as single precision.
DEFSTR	 Defines specified variables as strings.
DELETE	 Deletes specified lines in the current program.
DIM	 Reserves space for arrays.
EDIT	 Enters edit mode. This let you interactivly edit a line of BASIC
         code without having to re-enter it.
ELSE	 Used to direct execution to an alternate branch if the condition
         specified by the IF was not met.
ERL	 Returns the line number of the last error encountered.
ERR	 Returns the error number of the last error encountered.
ERROR(X)	 Generates error number x.
EXP(X)	 Raises e to the power of x.
FIX(X)	 Truncates x (drops the decimal portion).
FRE(A$)	 Returns the amount of free string space available.
FRE(0)	 Returns the amout of free memory that is available.
INKEY$	 Inputs a string value without pausing the program. Used in loops
         to catch a keystroke while performing other functions.
INP(X)	 Inputs one byte from port number x.
INPUT#-1	 Inputs data from casette tape unit #1
LEN(A$)	 Returns the length of A$.
LEFT(A$,n)	 Returns the leftmost n characters of the string A$.
LLIST	 Lists program to the line printer.
LOG(A)	 Returns the natural log of a.
LPOS(0)	 Returns the current position of the line printer head, in terms
         of characters.
LPRINT	 Prints to the line printer.
MID$(A$,F,L)	 Returns characters F thru L of the string A$.
OUTx,y	 Outputs byte y to port x.
PEEK(X)	 Returns the contents of memory location x.
POKEx,y	 Puts byte y into memory location x.
POS(0)	 Returns the postion of the cursor on the video display.
PRINT@	 Prints at a specified screen postion.
PRINTUSING	 Prints data according to a specified format string.
RANDOM	 Randomizes the random number generator.
RESUME	 Returns from an ON-ERROR-GOTO trap.
RIGHT(A$,N)	 Returns the last n characters of the string A$.
SGN(X)	 Returns 1 if x.gt.0, 0 if x=0, and -1 if x.lt.0.
SIN(X)	 Funtion that returned the sine of angle x, in radians.
SQR(X)	 Returns the square root of x.
STR$(X)	 Function to convert the number x to a numeric string.
STRING$(N,A$)	 Function that returns a string of n copies of the
                 single character contained in A$.
SYSTEM	 Places the TRS-80 in a mode that will allow the loading of a
         machine language program from cassette tape.
TAN(X)	 Function to return the tangent of angle x, in radians.
TRON	 Initiates trace mode.
TROFF	 Disables trace mode.
USR(0)	 allows access to machine language subroutine.
VAL(A$)	 Function that converts a numeric string to a number.
VARPTR(X)	 Funtion that returns the address where variable x is
                 stored in memory.