Is this happening on a specific document or all new documents. The setup of the manager area on the left is saved with each document; so that means the width of the manager area, whether it is split or not, etc. If it is a specific document, just double click or drag it up as you have said and save the document and then it should no longer be split the next time it is opened.
If it is all new documents, you must have it split in your document template, in which case you need to open the document, remove the split, and then save the document template.
I hope this helps,
This is happening in all documents, and dragging the menu up and then saving doesn't fix it when re-opening the document.
I double-checked the new templates I saved when Solidworks was reinstalled and they seem to have the menu on top. But I have been having trouble with templates recently, so it's possible that the template issue is also causing the workspace/menu layout not to be saved correctly.
Thanks for the suggestion! It's a good place to start if I have to escalate this to IT.