Another way to extend and get more creative concerning songwriting is to expand on one’s horizon concerning music making. I will give you two examples, one soft and one hard.
There have been many cases where a songwriter has become inspired just by learning new chords or scales and starting to experiment with these. As an example, someone who learns to play piano starts to see the beauty of extended seventh chords and start to use them in all kinds of interesting configurations. This leads to new songs and new compositions just by the force of exploring new musical territories. It always helps to learn new musical techniques.
The second example is someone who gets a new guitar or a new software synth, by exploring these new tools they get inspired and make new music, taking it into directions where someone didn’t expect to go earlier. So it indeed helps to update your setup from time to time, get a new toy and have fun.
Needless to say, if you don’t have a recorder hooked in, or work inside a DAW with the record button close by, all that inspiration will just dissipate into ether, and most likely you will forget it all and just have a vague memory what happened.