There is no integrated solution and that is the reason can not find. This was taken away do to them having to much control in the guts of Firefox and if issue with plugin caused issue with Firefox. https://www.howtogeek.com/333230/why-firefox-had-to-kill-your-favorite-extension/

Suggest Filezilla if need they full feature format and multiple panes to work in. I use it, is wonderful.

Please let us know if this solved your issue or if need further assistance.

Thanks for the information, and no, that does not solve my issue, and as far as I understand the current development environment, my issue probably won't be resolved in the foreseeable future. The same applies to another extension that fails to work for me now; New Tab Homepage, where the ability of an extension to load a local file (file:/// protocol) has been removed.

I appreciate there are practical reasons for these changes, not least of which is/should be user security, I assume Mozilla acknowledges that many users will find Firefox offers a less enjoyable experience, though I guess that's not an issue it feels it can afford to address without compromising its principles/ambitions.

Having read the responses of Filezilla developers to user concerns regarding security over the years, I'm not inclined to follow your recommendation, but I appreciate your response.