Misha,
Please correct me if I'm wrong, but it sounds like you are describing the fermata (pause) that occasionally occurs at the end of one song section and before the next section. In many popular songs in the Tin Pan Alley genre, such a pause is commonly found at the end of the introduction. The purpose of this sign is to tell players (a) to ignore strict timing and (b) to use their own musical judgement when holding the note. Strict timing then returns in the following bar. In classical music, the fermata is a very common occurrence.
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If what I've described sounds like what you are describing, the only way that I know how to do this is to interrupt the timing in some way, either by slowing the tempo or adding extra beats. My approach is similar to yours. I insert a chord cell or two and usually keep the same tempo. Sometimes I change the number of beats in the cell. Keeping the same tempo reduces the likelihood of audio artifacts occurring when I add the hold. I don't worry about getting it 100% correct in BIAB because I use my DAW to make any adjustments.
--Noel