Consolidate restore points into full for old backup?

I’m using Veeam Agent 6 (free).

I had to do a fresh install of my computer and did a file level restore to get my most important files back. Afterwards, I started a new backup chain.

I still have the backup from my old computer, which is 1 x .vbk  and 22 x .vib files. I’d like to keep just the latest restore point, synthetically merge it into a full backup (.vbk) and discard the old restore points. This will likely save 40 % of the space that the old chain currently occupies.

I know that Veeam Agent can do that with an active backup job and VBR can import old backups and I can manually trigger it. I hope I can do it with Veeam Agent and an old backup, too, somehow. How?