I had this problem too. Here’s what worked for me…
Lots of tutorial videos suggest that you have to select all the individual properties within the text animators before you save the preset, but I too, was losing all the custom effect ‘titles’ I had given to sliders & range selectors.
Instead, when I collapsed all the range selector/effects layers in the timeline AND then just selected the high level ‘titled’ layers before saving the new preset – the new titles were maintained and appeared when I applied the new preset.
I hope this works for you ; )