I haven't heard of the theme before but the filenames sound like they're probably related to an app so if you do have any apps already installed you could try disabling or removing them temporarily.
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Alternatively, you can try and use this chrome extension (https://chrome.google.com/webstore/detail/domain-blocker/ggdcjplapccgoinblmidpkoocfafajfa) and when you launch the theme editor open up domain blocker and block any URL that's not shopify. This will hopefully help what scripts and stuff get loaded in.
Finally, if the theme has inner pages with a lot of sections or the homepage is suuuuper lengthy and section filled this could also cause theme editor slowdowns
Thanks for that - I'll check that out tonight
I'm currently using Domain Blocker (link below), however, websites know they are being blocked which is a bit of a pain!
https://chrome.google.com/webstore/detail/domain-blocker/ggdcjplapccgoinblmidpkoocfafajfa