The answer is: NO!
All that has to be done in order to be able to use multiple filters within one message like
Recipient: Username+Filter1+Filter2+Filter3@gmail.com
e.g. Username+important+todo+notes@gmail.com
is that the filters need to be set up in a way that after the "+filter-extension" in the Filter Condition a * has to follow, being succeeded by the @gmail.com or whatever the extension is that google offers in your country.
Filter Condition:
to:Username+Filter1*@gmail.com
Username+important*@gmail.com
to:Username+Filter2*@gmail.com
Username+todo*@gmail.com
to:Username+Filter3*@gmail.com
Username+notes*@gmail.com
And that's it. From now on messages can easily be sent with multiple labels attached to them :-)