In Docs and Slides, there are the following two options:

Copy and and paste the math image directly in Google Docs or Slides. Then click on the copy. It will load in the editor, and can be edited as usual.

Click on the math that you would like to copy. It will load in the Hypatia Create editor. Inside Hypatia Create select all (with CtrlA) and copy. It’s important to use keyboard shortcut to make sure that the whole math is selected. Selecting with a mouse will sometimes select all visible content, but will miss delimiters that are needed when pasting. Then click somewhere else in Docs or Slides to start creating a new math inside Hypatia Create editor, and paste. Edit your math and Insert as usual.
In Forms:
 Click on Previous math dropdown and choose the math you would like to edit. If you have Pro features enabled, the list will contains up to 200 maths and for each math all its versions (edits). Edit the math and create the math image link as usual.