There is no limit on the size. If you notice one, please post the details to the support topic so that I can investigate.
- Custom keyboard shortcuts are already done for the next release
- Date & Time are already done for the next release
- I can increase the URL wrapper limit. No-one had asked for it before.

Update: There was a limit imposed by Firefox (not the addon). A bypass was added to the next version.

Adding title is possible .... I will see for the next update. :)

Firefox blocks some operations on some sites like AMO. That is hard-coded into Firefox at the moment and no way around it for a WebExtension type addon.

Please post your support question to the support page (with details)