Since hotkeys don't seem to be documented anywhere, here's a list of the ones I know. This is a WIP. I'll be adding to it as I remember/find more. Contributions are very welcome.

I presume hotkeys may work or not depending on the browser (I'm on Brave, and a few don't work), and some keys may also be different on keyboard layouts from different countries (usually the symbol keys). One example is the comment/uncomment key. I'll list what I know from my keyboard, followed by any alternatives I know of in parentheses.

@HomineLudens pointed out on Discord that "the editor is based on Ace", so some or many of its hotkeys are the same. I'll be copying them here as I can.

(LMB, MMB and RMB are the Left, Middle and Right mouse buttons)

The list:

• code editor

  • Misc

    • F1 - pops up a menu with actions (and hotkeys) (make sure code editor is focused)
    • F2 - toggle fold widget (not sure what that means, I pressed it and it folded the code-block around my cursor)
    • ctrl , - show text editor settings
    • ctrl Z - undo
    • ctrl Y (ctrl shift Z) - redo
    • ctrl F - find (make sure the code editor is focused, or the browser's finder will pop up instead)
    • ctrl H - find & replace
    • ctrl C - copy
    • ctrl X - cut
    • ctrl V - paste
    • ctrl ~ (ctrl /) - comment/uncomment line
    • ctrl shift ~ (ctrl shift /) - block comment/uncomment
    • ctrl up/down - scroll text up/down
    • ctrl shift up/down - cycle numbers under cursor, or certain words (get* <-> set*, maybe others) under cursor
    • alt E - go to next error
    • alt shift E - go to previous error
    • ctrl \ - move cursor to corresponding bracket (when cursor is next to a bracket, and on the inside of both)

  • Line

    • ctrl L - go to line
    • ctrl shift D - duplicate line downward
    • alt shift up/down - duplicate line up-/downward
    • alt up/down - move line up/down (doesn't work for me because one of my browser extensions uses it)
    • alt left/right - move cursor to start/end of line
    • ctrl D - delete line

  • Multicursors

    • ctrl alt up/down - add a cursor to the line above/below
    • ctrl LMB - add a cursor to the clicked line
    • ctrl K - select next occurrence of the selected text (or of the last one selected in this way, if nothing is selected)
    • ctrl shift K - select previous occurrence of the selected text (or of the last one selected in this way, if nothing is selected)
    • ctrl alt K - select all occurrences of the selected text
    • ctrl alt left/right - add previous/next occurrence of the selected text to the selection
    • alt LMB drag - select over multiple lines with multicursors

• sprite editor

  • Misc

    • ctrl Z - undo
    • ctrl Y (ctrl shift Z) - redo
    • ctrl C - copy selection, or entire sprite if no selection
    • ctrl X - cut selection, or entire sprite if no selection
    • ctrl V - paste
    • space LMB - pan view
    • scroll wheel - zoom view
    • LMB(MMB) - use selected tool
    • RMB - quick eraser
    • alt - quick color picker

  • Selection tool

    • LBM drag - move selection
    • shift LMB drag - drag the selected pixels
    • alt LMB drag - drag a copy of the selected pixels

I think it should be added to the documentation :)

Another thing: When highlighting text, and pressing '/"/(/[/{, it surrounds the text with those characters (in the case of the parenthesis/square brackets/curly brackets, it puts the closing version at the end). If you press Tab while highlighting code, it indents all the lines you selected instead of replacing them with a single tab

Under code editor, then line, alt backspace deletes everything to the left of your cursor.