On the Transactions page, the button "Add to X account" changes to "Add transaction" when the browser window is reduced to a smaller screen width. When that happens, the quick-add options to the different accounts disappear from the dropdown menu, which will then only show "Create transfer" and "Create from recurring".

Also, if the window size is significantly narrow, the Quick search appears beneath the 'Add Transaction' button, and the drop-down menu hides behind it.