I have followed the instructions for deleting the trash folder, selecting all files that have trash in them from my ImapMail folder in Thunderbird Profiles and restarting Thunderbird

I don't really understand what that means and what exactly you did. With IMAP you should be really careful what you're doing while online, particularly deleting stuff. Everything you do in Thunderbird is mirrored on the server instantly , so it's very easy to erase messages or entire folders you didn't want to delete in the first place.

What instructions did you follow? Please post a link.

What was the Thunderbird restart supposed to do?

but the Trash file appears corrupted upon reopening (multiple tries over the past few weeks). It also appears with a subfolder X that is corrupted and that I cannot delete.

Can you log on to your account via webmail and delete the contents of the Trash folder on the server?

I followed instructions from this link: https://www.nucleustechnologies.com/blog/cannot-delete-messages-in-thunderbird/ But I also looked at an early suggestion from this site. Both said to close Thunderbird before deleting the trash files, and then restarting.

My university no longer supports webmail, and I'm hesitant to delete the trash folder from Outlook, is that what you are recommending?

Your instructions look pretty much like being copied from this support article: https://support.mozilla.org/en-US/kb/cannot-delete-messages

Have you tried to right-click Trash in the folder pane - Empty Trash?

I have followed the instructions for deleting the trash folder, selecting all files that have trash in them from my ImapMail folder in Thunderbird Profiles

Profiles? Are you saying you're having multiple profiles? If so , do all profiles have the problem?

What exactly means 'selecting all files that have trash in them'? Which files exactly and in which profile? Please be specific.

I'm hesitant to delete the trash folder from Outlook

You really need to be more specific what you mean with 'Outlook' here.

I received the email support and will answer that here.

Correct, that is the set of instructions I used.

I'm on a Mac, so I used control+click to empty trash and delete the trash files in the ImapMail folder, but this didn't change anything and the Trash folder is still corrupted (see attached)

Profiles is the name of the folder in Thunderbird (see attached)

Outlook is the web-based Microsoft mail program (used by my university). I am using that while I am having this issue in Thunderbird because I can delete messages there. I don't really care for the platform so wanted to continue using Thunderbird unless I can't solve this problem

I used control+click to empty trash and delete the trash files in the ImapMail folder

My last attempt: what files exactly?

Outlook is the web-based Microsoft mail program (used by my university). I am using that while I am having this issue in Thunderbird because I can delete messages there.

Then you can probably also empty the trash via Outlook webmail.