Sometimes my noting tends to become too effortful. Noticing that effort too and letting it be helps, but sometimes I find it useful to explicitly bring compassion into noting in order to be more compassionate towards myself and things that are noted.

- May I be happy and free of suffering even when feeling, thinking, feeling, wanting, seeing, ...
- May I see "as it is" this feeling, thinking, effort, ...

It also seems to be quite useful reminder during intensive day at work:

- May I be happy when planning / discussing with these people / whatever is happening

Have others tried similar things?

I have found that tuning into the fact that phenomena arise by themselves (and awareness is aware by itself) can be helpful when noting takes too much effort and becomes stressful. Instead of 'hitting' phenomena with noticing mind as quickly as possible, I take a step back and notice whatever appears in awareness, paying attention to the fact that appearance and noticing happen without me having to do anything, without any effort.
This can be a great relief at times, but there is an increased danger of spacing out (which, when it happens, can be counteracted through more engaged noting).

Edited to add: This could be considered as a way of noticing anatta. It is somewhat similar to the metta-noting approach you describe as it involves relaxing one's grip and focusing on positive things (feeling good), and thus can bring about a positive feedback loop of noticing-relaxation-feeling good-more noticing ...

Nice point.

It also helps with subtlety and speed, as reality can go much faster on its own than the linear, noting mind, and that gets us to depths of complexity, inclusiveness and naturalness that are helpful.

That describes pretty much what I'm doing. It's great to be feeling normal but mentally healthy. When I verbally note I start thinking "who's intending to note?"

Yeap, I call it the "metta-sanna" . I applied metta until the sensation settles down into an zero aversion state. The idea is to found the positive aspects of the noted phenomena to counterbalance the negative ones. Another tool to slow down the restlessness is to insert some minutes of Shinzen's "gone" noting, that is to note only the vanishings and enjoy the (short) restful state until another phenomena arises.