I've recently done it, but "only" had 2 dozen VLAN's, so I did it manually, but it is probably automatable.
How I did it was as follows:
In Datacenter -> SDN -> Zones -> Add a VLAN-type zone, configure it to the Linux-bridge that you want your LAN traffic to be on. The name of this bridge needs to match on all your Nodes, but what this bridge then connects to (bond or direct to a device) does not matter.
Then under the VNets tab, create a net, give it a name, optionally a descroption/Alias to further know what's what, select the just created zone, and set a tag (do not set vlan aware)
Rinse and repeat the above, then finally in the SDN-tab itself, don't forget to apply.
With that I can set all VLANs, and for the untagged VLAN I select the bridge itself, in the rare cases that we need that one.
For the automating, one route you could do: The config for the SDN is saved in /etc/pve/sdn/vnets.cfg, create 1 or 2 VLAN(s) fully manually, then use some script-foo or excel-foo to fill in the rest from the text-based export of your VLAN's or your documentation.
A tip for the excel-foo:
if you have a CSV with 2 colums, ID and Description, in column C you could put something like (vmVLANs is the name of my zone, and the name of my net I did the letter V followed by the tag):
=CONCATENATE("<ENTER>vnet: V",A1,"<ENTER><TAB>zone vmVLANs<ENTER><TAB>alias ";B1;"<ENTER><TAB>tag ";A1)
Then copy/paste the resulting lines to a notepad++ or similar and replace the <ENTER> and <TAB> text with their corresponding thing, then copy all THAT into the vnet.cfg file, save, re-open the SDN-page and apply it
