This is not so obvious but it works. When you click on 'Attach' and the 'Attach files' window opens, at the top it may show a default location, perhaps the last place you attached a file. If you click in that area, it should highlight all that text, then start to type and as you enter a / it should offer a drop down to select or keep typing. Do not use the 'search'. Example in a Windows OS after I click on 'Attach' It might show last location eg: This PC > Documents > Ancestry When I click in that area after the word 'Ancestry' , the text changes show actual path directory and it is now highlighted, so I can edit. eg: C:\Users\UserName\Documents\ANCESTRY If I clear it and start to type: \Users\ A drop appears offering me a list of options including \Users\UserName - So it acts as a guide as I'm typing. As I type it offers more drop down options, when it gets to the actual folder containing the file, press 'Enter to select that folder and all the files are displayed. Alternatively, if I have a text copy of the path directory which I can use, then copy it and paste it into the address area, but do not include the filename bit; just the path to the folder that contains the file. Now go down to the 'File Name:' section and either type the file name or click on the file to select it so name is now entered in the 'File name' at the bottom and click on 'Open'. In Linux Ubuntu - in Write' window - click on 'Attach'. Don't click search. Just start typing the path. It'll automatically switch to a text box the moment you hit / But if you find you can only get as far as the folder that contains the file - like me on a Windows OS, then go down to the 'File Name:' section and either type the file name or click on the file to select it so name is now entered in the 'File name' at the bottom and click on 'Open'. Basic method - click on 'Attach' navigate to folder, select file and click on 'Open'. Or perhaps you have keywords set up, so that if you have the word eg: 'attached' in the content, then a reminder pops up at the bottom with a 'Add Attachment' option which is basically the same as clicking on 'Attach'. There is also the ability using right click on attachments to reorder them. '''In current version 91.1.2, ''' ...those methods are still the same, however there is also an improved ability to drag and drop files. All attachments are now shown below the composed email. The ability to reorder attachments is still available, but as they are not shown in list format, it's not so intuitive. There has been a bug created regarding this asking for attachments to be moved to the top right again but that does not mean it will be acted upon. See info: * https://support.mozilla.org/en-US/kb/new-thunderbird-91#w_new-user-interface-for-adding-attachments * https://bugzilla.mozilla.org/show_bug.cgi?id=1731186

I believe that in Ubuntu and GNOME desktop, this 'path' bar is not visible by default. You have to trigger it by starting to type the path.