This paper reports recent advances in the development of a symbolic asymptotic modeling software package MEMSALab which will be used for automatic generation of asymptotic models for arrays of micro and nanosystems. First, an asymptotic model for the stationary heat equation in a Micro-Mirror Array developed for astrophysics is presented together with some key elements of its derivation. This illustrates the mathematical operations that need to be implemented in MEMSALab. The principle of operation of this software is to construct models incrementally so that model features can be included step by step. This idea conceptualized under the name "by extension-combination" is presented for the first time after having recalled the general functioning principles. A friendly user language recently introduced is also shortly discussed.