I just added a new Firefox installation to my Firefox account. I did so by clicking on sync settings, in order to have a chance to modify the settings before sync started. As expected, I was first prompted to sign in to my Firefox account. I was then invited to install Firefox on my smartphone, which doesn't interest me. Since I found no option to dismiss this completely, I clicked on "remind me later". Then, instead of opening Sync settings as I expected, Firefox began to sync immediately. In fact the activity blocked Firefox for a while, preventing me from accessing sync settings at all. After getting into the settings, I disabled some things in sync settings, but don't know what undesired "cross-fertilization" may have already occurred between my Firefox installations. How can I find out? How can I get control of Firefox's syncing behaviour? There is a prominent "Sync now" button in the sync settings, but this only makes sense to me if there is some way to stop automatic syncing and make Firefox wait for me to click the button. How can I suspend automatic sync and make Firefox wait for a manual sync command?