It is possible make slide to respective in frequency sample on multisample instrument by using Gxx command? In current version Gxx just slide pitch of current sample.
C4 G30 to C6 just pitch up C4 sample and not slide to C6 sample in C3, C4, C5, C6 instrument. I hope, an example is understood. 
I guess you’re looking for some kind of key-zone based morphing or cross-fading?
Because, you’re quite right - samples, once triggered, will remain the same even as you’re transposing them.
And I think in most cases, this makes sense. Because some unwanted issues could actually arise from doing somecross-fading - such as signal cancellation (due to phasing between the two waveform).
Also, the two samples might simply be part of a kit that shouldn’t morph, ever. For example, a drum kit where you would want to wild-pitch the hihats, but never-ever turn them into a tom or clap. Or a synth preset such as this one, where each key represents a unique and distinctive timbre.
So I don’t think the idea is a bad one, but it needs to be implemented carefully, made optional somehow.
even if you had very similar samples - like multiple keys from a piano spread along keyzones - you would have problems like you have when crossfading samples. I.e. the passage where they overlap would most probably muddy and different in volume to the straight passages. This is because the samples are most probably not phase aligned, and it would be tremendously difficult to somehow make them perfectly crossfadable.
For such extreme portamentos you could still “fake” the crossfading yourself. Normally an octave works quite ok for me. But if you really want the samples switched on a special glide, i.e. because it sounds like mickey mouse or damp, you could make two tracks for the glide and crossfade them at the right point.
I want to do with multisample instrument, something like monosynth in legato mode , but how I see, its possible only with one sample instrument. Viva oldskool !
I think it would be kind of possible, if you for example only wanted to crossfade 2 waves over a certain note/key/freq range, maybe even more up to 12 or so. With big hacking and improvisation while building the instruments! Not like it would be supposed to work easily. Also you would have to forget the normal portamento commands und use something crafted via formula device. I have a solution in mind if you are interested, but it really needs some work to be set up, and for each possible behaviour probaly much work has to be done. So you would have to tell me what kind of instrument you would have in mind, how it should behave. Remember monophonic only and none of the U/D/G commands will work, but glide/legato/bend could be crafted differently and similarly easy to use (or even automatic glide with constant time to reach target notes, which I personally prefer over tracker style portamento).
But still such solution would suffer if the crossfaded waves aren’t 100% frequency and phase aligned (piano samples for example are most probably not! Singe cycle saw and square of same length would be), they may just change timbre/tone. Else it would go muddy on the transition between the samples.
Thanks for help, but all that cheeki breeki formulas not for me ( I’m not a friend with mathematics). I wait for normal portamento option in next(s) Renoise version, it’s not very complicated to do, I think, because I find this in freeware samplers like Tx16wx and Grace. So it is just dependent from developers. I wonder, Redux have this or not ?