Hi Kyri,
To test on our side, we'd like to confirm the following information:
- Regarding "An extra space keeps appearing at the end of a line whenever I paste any content into the "Advanced Find and Replace" dialog box." Did you perform the steps below?
- Open Word.
- Click View>Navigation Pane>Magnifying glass>Settings button>Advanced Find&Replace>Paste content in the Find what box in
Find and Replace window like below:

If it is not your situation, please clarify with detailed steps.
- About the copy-and-paste action, did you use Command+C and Command +V
?
- For "a list of wildcard searches" you mentioned, please provide a sample example in the private massage I sent to you. You can check the message via the link below:
https://answers.microsoft.com/en-us/privatemessages/list
- Regarding "Seem to be encountering a bug since a recent update", please provide the detailed information of Mac and Office.
Mac version(Apple icon>About this Mac>Capture a screenshot of the popup window)
Office version(Word>About Word>Capture a screenshot of the popup window)
Meanwhile, could you clarify if it is Mac update or Office update?
Regards,
Tina