SDL Support wrote:
If you use the upgrade TM facility in Studio you can add multiple TMs of various formats, and convert them to an SDLTM. You can group these by language, one to one, or customise how you want them merged.
During this process a tgempoprary file is created for each TM in TMX format and there is an option to retain this rather than delete it.
I don't know what the limit is for the number you can do at any one time, but if you have Studio then perhaps this will help?
Hey Paul thank you, I'll try what you've said.