Try this: congifure your junk folder in AquaMail as spam (long press on account name, options and folders, folders, fetch your junk folder, synchronize it as spam)
I have detailed the process to make a folder behave as spam (written in bold blue in a specific answer to one of your questions)
You can make Spam folder appear in AquaMail, and work exactly as a spam folder (i.e. messages stored in that folder will not affect the total count of messages, will not appear in "Smart Folder" - really a perfect ability in AquaMail, etc.)
For that, go to account list (in AquaMail), long press on your account name (for which you wish spam folder to appear), and:
- click on "Options and folders" (Paramètres et dossiers)
- "Account options" (Paramètres compte)
- "Show "Other folders..." (Afficher "Autres dossiers...")
- return to previous screen
- go to "Folders" (Dossiers)
You will see all IMAP folders of your server. One of them is Spam folder, you click on it, and choose Synchro as spam "Synchroniser comme courrier indésirable"