Please provide more details to your bug report and possibly some screenshots, as the current explanation is difficult to understand to due lack of info.
This is what you're being presented with, when you "right click" anyplace the xfce4-indicator-plugin is, no matter on which icon you do that on:
And is what you're being presented with, when you're right clicking on caffeine/qqmp/redshift icons respectively when using xfce4-panel's "Status Tray Plugin":
caffeine
qmmp
redshift
And I forgot to mention that his happens on:
debian testing/unstable (buster/sid) with xfce4-indicator-plugin: 2.4.0-1.
Thanks. Which icons do you see in the indicator plugin as I've never seen anything in it other than pidgin? From my understanding this is the correct behaviour for this plugin, which is different from the behavior of tray icons in the status tray and notification area plugins.
This is a matter that needs some research being done.
I have a lot of icons when I use various programs but there is not universal to have them all showing up, except what seems to be xfce4-indicator-plugin but this makes some programs unusable because you can't get to their "context menus" and even the default behavior on clicking on their icons change.
I'll make a table with the behavior of each program if you need it, and report back but for now here is a non-exhaustive list of programs I use and do show some icons and they are crucial to their functionality: caffeine, discord, element-desktop (aka riot.im), qjoypad, qmmp, redshift
I did that research I was talking about earlier regarding my use case, and here are the results:
xfce4-indicator-plugin (2.4.0)
xfce4-statusnotifier-plugin (0.2.3)
xfce4-panel's "Status Tray Plugin" (4.16.2)
audacious (4.0.5)
Yes
Yes
Yes
caffeine (2.9.8)
Yes
Yes
Yes
discord (0.0.14)
Yes
No
No
element-desktop (1.7.24)
Yes
No
No
network-manager-applet (1.20.0)
No
No
Yes
qjoypad (4.3.1)
Yes
No
No
qmmp (1.4.4)
Yes
No
Yes
redshift (1.12)
Yes
Yes
Yes
The trouble arises around the usage of: qjoypad, qmmp which they do not "unhide" their windows, to which behavior I'm used to expect, when I left click their "indicator icons". For example if you want to unhide those programs' windows you cannot do it once hidden and you have to improvise other methods to get to it.
Something funny just happened, which I don't know how it did happen, as I was updating the table above I forgot to include audacious and I did re-add all those items in the panel to check its behavior and... BOOM! everything showed up in xfce4-panel's "Status Tray Plugin" which I configured to my taste.
I guess it has to do with me clicking on "Clear Known Items" button.
But, bottom line, if XFCE's plans are to deprecate all those in favor of xfce4-indicator-plugin I believe there should be an option to toggle/allow more option to the user regarding: "Menu is primary action" and to clarify this I mean that the user should be able to interact with those icons with either "left click" and/or "right click" and should be left on their preference.
Glad to hear your issue was resolved. I don't think there is any plans to deprecate the indicator plugin. I just don't use it and always remove it from my panel.
Not it's not resolved, what I'm saying still applies to: xfce4-indicator-plugin it needs to allow left clicking the icons as some applications have some functionality to it which is not substituted by showing a context menu.
Onto my use case, something's must be misconfigured on my system and I'm asking on how to determine so, as of today, none of these showed their icons to xfce4-panel's "Status Tray Plugin": discord, element-desktop, qjoypad which they did some hours ago and since then I haven't tampered with related configuration files or settings in any way.
What has happened in between was that: my monitor turned off, xscreensaver worked for a while, then the display went to sleep, then turned back on again. Maybe I should file another issue to xfce4-panel? I'll do that later.