I wasn't able to find a one-click solution for what you want, but I think that the USB Formatter [mintstick] service menu for Dolphin might be close to it.
To add the service menu to Dolphin's right-click menu you first have to install
mintstick. Download and install its latest version (1.4.4) in your
Downloads directory using the following command:
wget -O ~/Downloads/mintstick_1.4.4_all.deb http://packages.linuxmint.com/pool/main/m/mintstick/mintstick_1.4.4_all.deb
Install it using:
sudo apt install ~/Downloads/mintstick_1.4.4_all.deb
Download the USB Formatter [mintstick]
.desktop file from here.
Supposing that you have saved the file in your
Downloads directory, copy the file in
mkdir -p ~/.local/share/kservices5/ServiceMenus/ && cp ~/Downloads/FormatUSB.desktop ~/.local/share/kservices5/ServiceMenus/
The above command will also create the required folders if they do not exist.
You should now be able to find the option to format a USB with
mintstick (USB Stick Formatter) by right-clicking in a directory → Actions → Format USB.
This service menu also adds an option to also have the Format USB option in the device notifier, but as the author of the service menu notes:
Note: in order to display the "Format USB" option in the removable
device notifier, you must have pressed the "format usb" button in the
dolphin menu at least one time.
Also have a look at the related video to see how the service works.
Note: I haven't tested the above, since I don't currently have an installation with KDE. Any feedback is appreciated.