That's why serato allow you to edit the beat grid

Right, you can't set a new downbeat without affecting the tempo. But you can can give the break another bpm so the first beat after the break gets a downbeat...

That's fine and dandy with some tracks, but other tracks have strange phrasing or breaks that are too small to beat grid in such a way. I have plenty of songs where the 2nd or 3rd beat becomes the new downbeat just before the drop (Black magic part II - KTN and Wild Life - Kevin Hunter come to mind). Playing with the tempos to get the downbeat to line up with the second beat is a nuisance as sometimes I have to set a beat marker on the last downbeat, change the tempo in between to something like 2x or 4x the original tempo (which isn't always possible) and then set another beatmarker on the new downbeat. I can also jump back to the downbeat before the "break" downbeat, and warp the tempo to line up with the drop (which is what I usually do), but then mixing out/in cohesively during these breaks becomes an annoyance. It would be great if I could set an independent beat grid that had nothing to do with the first one and wouldn't warp it to fit the new down beat. Traktor's beat grids are able to do this (though they have their own limitations like not handling transition and unquantized tracks well), because they are actual beat grids not bar grids like in SDJ. That's my rant. Please allow me to choose whether to set beat or bar grids Serato, Thanks! All the beat warping stuff is great though. (Just switched from Traktor)

I'm not sure if this helps you or not, but I found a good workaround for those "grid transitions". I keep the downbeat markers where they should be. But with sync engaged, you get that horrible tempo change sound. I just use FLIP to skip that part.

I don't have the cash for the flip expansion. Either way, if I was gonna cut the parts out I'd just do it in FL Studio and label it as a quantized edit or something. I also don't use sync very often anyway, and if I do it is simple (tempo) sync. I just like having the visual grid to help my ear with the beatmatching. Two senses are better than one. (And quite honestly some of it is just OCD)

yes, but i use sampler sync to the song sometimes, and whand the beat grid is false, it's not funny

There is a solution siddeonemada. Turn off sync for those kinds of transitions or don't mix in/out from those points. I'm not really a sync hater, but everyone needs to be able to match and adjust by ear. Sometimes beatgrids fail, and your ear is the only thing you can rely on, this is especially true in live gigs. I feel your pain though, it's like trying to mix Strobe - Deadmau5 at that part when the downbeat slowly changes from the first to the second. I just don't do it, unless I know I have and outro from the previous track with no snares.

i don't need sync for song, just for the sampler, it's impossible to adjust the sampler bpm without sync with serato

Ahh, then you are probably up the creek my friend.

I think it's impossible to have those complex tracks gridded automatically. You will need AI built in for make this happen ;)

For me I was able to grid every track in my library. But some took a while! I have tracks that start for example with 134 bpm, go up to 300, down to 90 and back to 134. No problem at all.
I color code those tracks with red so I can instantly see if I need to turn off sync...

That is a magical work around serkan, I am going to do that as well thanks! Color coding.... totally forgot about that feature haha that is genius.