It depends how you want to share... the "Copy Map" button will put some text like this in your clipboard:
o224To13to15Tsnw4nw4nsTo14str11t3so15srOw3rw3rotso16nRsOr5sotno16wrwOwesewRwtwo16wrwowno3nwrwtwo16wrwoeo5erwrwo16nrwr3o3r3wrno16wrwreo5eowrwo16wtwrwno3nwowrwo16wtwRwesewOwrwo16ntosr5OsRno16storw3rw3Orso15st3r11tso15tsnw4nw4nsTo28To225G450
If you copy that and paste it into the editor, the layout will load.
Alternatively, if you want to paste a direct link to your map, use Copy URL, then paste the URL, it will look something like this:
https://html-classic.itch.zone/html/14772968/GrimPlanner/index.html?map=o325eo28...
Note that you need to run it from the proper link to access clipboard features.