for having a rtl virtuemart you should make 2 steps

1-first is to have your admin language to have your customized rtl language

2- second is to copy the virtuemart language pack that contains rtl and is provided in virtuemart official website available for download

if you change the default language of the admin area of joomla to that custom rtl language then the virtue mart will automaticly changed to have that specific language providex in the language pack of virtuemart that is coresponded to the language defined in administrator language

if you had any more question do not hesitate to ask this by posting a comment

I would be thankfull to answer

thanks

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1. Fixing tabs in virtuemart forms for RTL languages