The entire express network needs an increase in frequency - ideally for the Glasgow services bring back the pre-Covid set up and have the X26 return and the X27 doubled; if not at least run each once an hour at twenty minute intervals from each other, providing a 20 minute frequency between Glasgow and Halbeath.
On the Edinburgh side, the X55 could definitely benefit from returning to a 20 minute frequency. I suggested this further up the thread but as the topic's come up again, I think a peak-time express between Edinburgh and Halbeath via Ferrytoll would definitely be of use - by far some of the busiest stops on the Edinburgh express network are Ferrytoll and Halbeath and from my experience it's pretty common to have 10-20 passengers get on/off at the park and rides at peak times. Additional capacity along this corridor will help passengers travelling further afield to actually catch the bus they want to, and give more space for passengers using the other Edinburgh stops, as it's all too common for buses to leave Princes St or Queensferry St completely full, leaving passengers at Craigleith, Blackhall or Barnton stranded (this has happened to me several times!).