How to convert processed 2D wavelet subspace back to the form of original 1D result

Hello all, I have a question regarding the wavedec2 function.

My goal is to perform some algorithm in the approx and each detail sub-spaces in their 2D form. There is a semi-convenient way (though most programmer would definitely prefer entering '1,2,3' instead of 'V,H,D') to extract the coefficients and recover the sub-space (in 2D) from the 1D result (appcoef, detcoef). But is there a convenient way to put the processed 2D sub-space back into the 1D composite space? Or I must count the indices myself?

Thank you