Maybe that's useful info for someone else as well. It also made me think there may be some other things about items on the Xfce panel that are not immediately obvious, particularly to newbies. For example:
(1) As stated above, you can drag an item from the Add New Items list to wherever you want it on the panel. Also, instead of right-clicking an item in the Whisker Menu, you can drag it straight from the Whisker Menu to either the panel or the desktop to add a Launcher for that particular app - and no, it doesn't remove it from the menu! If it won't fit between two existing launchers, you can hold down Ctrl while dragging to give slightly finer control. Worth noting that there still seems to be a bug where sometimes you go to add a launcher to the panel and find that it's added a different one (often Firefox or Terminal) but it works when you try again.
(2) If you want to move an item already in place on the panel, there are two ways of doing it. You can right-click, select Move and then drag and drop it to the new position. Alternatively, you can right-click and select Panel Preferences... then go to the Items tab which lists all items currently on the panel, select an item and then walk it up or down the list by clicking the arrows on the right. This corresponds to left or right on the panel and the chosen item will move along the panel accordingly.
(3) You can space items out by adding one or more Separators to the panel. By default they show a vertical line so you can see where they are - but right-click, select Properties and you can change the style to Transparent so it is invisible. You can also tick Expand so that it widens out and pushes items on either side further along the panel. If you ever find that your clock and other right-hand items have suddenly moved to the middle, it is probably because you have accidentally deleted an expanded Separator in the middle of the panel - or maybe added one at the far right of the panel! To see where all the Separators are, look on the Items tab in Panel Preferences, which is easier than right-clicking at random all along the panel!
(4) Generally you can right-click on a panel item and select Properties to bring up the settings for that item. That doesn't work for what Xfce calls the "Window Buttons" i.e. the rectangles which show all the windows currently open (or minimised) on the desktop. Here you need to hold down Ctrl and click on the Window Buttons to show the Properties option. Alternatively, you can use the other method of accessing settings, which is to go to the Items tab in Panel Properties and either double-click on the relevant item or just select it and then click the edit icon.
(5) If you ever lose the Whisker Menu and have to re-add it, it may show up without its Mint customisation. This post may help restore it to how it was:
viewtopic.php?p=2416787#p2416787
(6) This help page for the Xfce panel includes a list of plugins that can be added:
https://docs.xfce.org/xfce/xfce4-panel/start
Some (eg the Weather plugin and Places plugin) are already installed in Mint, so you can simply go to Add New Items... and find them in the list. Others (eg the Netload plugin) have to be installed first and then they should appear in the Add New Items list.
And finally -
(7) Sorry, I haven't a clue why Linux calls the taskbar the panel...
