Is it possible to manually connect two devices or objects on the map with the new SolarWinds Platform 2023.4.1?

Yep - they each just need to have an interface (and that's not strictly true either).

Details are on the support site: Create and edit Intelligent Maps (solarwinds.com)

Yep - they each just need to have an interface (and that's not strictly true either).

Details are on the support site: Create and edit Intelligent Maps (solarwinds.com)

Doesn't this write tables into the DB?

Yes.  It adds a manual relationship between the two interfaces.  You can choose to that the relationship reflected only for this map or allow the rest of the environment to use it.  There are pros and cons to each depending on the need.

We are still working out all of the SNMP issues on each device, but in the meantime, can I connect two devices without using the interface custom topology connection? Simply put, can I create/draw a line between two devices not using the interface custom topology connection?

I mean - you can, but the line wouldn't hold any significance in respect to the topology.  Interfaces aren't the only "connections" between elements.

If you do elect to go with interfaces (most common), you'll need at least one of the two nodes having interfaces monitored.

SNMP polling issues?  Personally, I'd get that remedied before I worried about making "pretty" things.