so.
basically i want to delete a number of characters (that vary) by defining their position from the END of the file name
Indeed with almost every app, the file name has a highly variable content and length, so that defining a string position from the start of a file name can often be problematic, eg music track names as in this case.
and simply Replace does NOT have any capacity to define a position from the END of a file name
frustratingly, the ADD functions DOES have such an option, albeit a bit kludgy - the From parameters WILL take a NEGATIVE value - which can be used to select a position from the end: the Replace function does NOT have this possibility.
so in this case, i can C&P one example ...
Anneke Van Giersbergen - Time After Time [La Scene Bastille] [2012] [136kbits 48kHz] [conv-96kHz] [619 min] [868 kbps 96 kHz] [conv-192] [norm-aimp-0db] [619 min].flac
so in the above name, i want to delete a redundant and old data about the encoding (as should be indicated in bold). if that data/text string was always the same, no problem of course - but it isn't.

(and i cannot rebuild the name from scratch as the same old data is in the Title field too.)
so any brilliant ideas, anyone?