This is a continuation of proposals 2017/1-228, 2017/1-343 and 2017/1-553 - Spectral modelling of supernovae. The paper presenting the spectral code JEKYLL will soon appear in Astronomy & Astrophysics, and we expect to submit a second paper with application to Type IIb SNe early in the autumn. We are also working on a third paper on Type Ic SNe which we estimate to be completed late this year. During 2017 and 2018 we have presented the JEKYLL code at several conferences, and received much attention for its capability to produce realistic simulations of SN spectra and light-curves. This is a long term project and we aim for a LARGE proposal for the first half of 2019. However, until then we will ask for a continuation of our MEDIUM proposal. In addition to the ongoing projects, we are planning to model superluminous SNe and Type IIL SNe, as well as a study of the effects of different approximations commonly used. Superluminous SNe are rare and poorly understood, in particular with respect to the powering engine, and using JEKYLL we can simulate spectra and light curves for different scenarios in unprecedented detail. We also aim to study the effects of different approximations used in SN modelling in relation to e.g., non-equilibrium effects and hydrodynamical mixing, which as shown in the first paper may have strong effects on both spectra and light curves. Modeling with the JEKYLL code is an important complement to the observational activity of the supernova group in Stockholm.