How do people get around the 3 Tiers of Sponsorship if they have more Tiers?

no, does not look like you can edit sponsor tiers.

If your client is still expecting to have 4 tiers and you’ve found no acceptable workaround, consider asking Zoom Event Consulting Services for assistance:
https://support.zoom.us/hc/en-us/articles/207362486-Zoom-Online-Event-Consulting-Services 

Be prepared to pay by the hour for their help – but they’re the insider professionals!

We did this too before we knew about the constraints.  We ended up combining tiers into 3 (Platinum/Gold, Silver/Bronze, Community), and then we gave additional benefits (podcast/webinar highlights) outside fo the tier system to make up for the discrepancy.