Which country to apply through?

I am seeking advice on future visa application. The question at hand is whether I should apply through countries where I have previously applied, or I should just apply through any country that will be my next port of entry.

Here's my situation: Chinese citizen, moved to the UK last year for work.

First Schengen visa was from France in 2017 (3 months, multiple entries, 30 days total). Second was early this year from Bulgaria (I asked for two entries and they gave me exactly two, 10 days total). I had EU residence card twice (France 2014-2016, Netherlands 2022-2023) for study and work reasons.

I recently applied for a short-stay tourist visa through Denmark, requesting a one-year multiple-entry visa in my cover letter, but was granted only 3 months, multiple entries, 45 days total.

I am writing to ask for advice. Through which country should I apply for my next Schengen visa if I hope to obtain a longer-term visa, like one-year? As I work in academia and travel frequently for conferences, applying for a Schengen visa for each trip is quite inconvenient. I have three conferences next summer (Italy - France - Italy), which I mentioned in my cover letter to Denmark but of no help lol). I have a clean travel record and sufficient savings.

Thanks for your insights!