What problem does this address?

As part of the fifth call for testing for the FSE Outreach Program, the following feedback came in. Of note, this is was translated from Japanese and is not the original text:

When selecting the category of the Query block, it would be nice to be able to select from a list of existing categories instead of suggestions from input. Because I do not remember all the categories.

Another person later brought up the same feedback:

I believe another tester mentioned this too but I think it would be helpful to have a list of the categories I can choose from or a drop down instead of relying on the user to remember their categories.

What is your proposed solution?

List the categories in a way that matches the post editor. It's not clear to me though if this might cause performance issues so, if that is the case, feel free to close this :) but I do think this might be a helpful addition to consider.

Current view:

Categories in the post editor: