MUSE synthetic maps, from PLUTO 3D MHD model of the multi-threaded magnetic flux tube discussed in Section 2. Here we show the tube structure at time ∼180 s after the onset of the instability and with the loop in off-limb configuration (LoS along the $\widehat{\mathit{y}}$ direction). From the top, the first row shows the intensity of Fe IX, Fe XV, and Fe XIX emission lines. Second row shows the related line shifts instead. Third row shows the non-thermal line broadenings. In the Fe IX Doppler shifts and widths, we only show the pixels where the line intensity exceeds the 5% of its peak ($I_0>0.05I_0^{\text{max}}$). We show Fe XIX observables rebinned on macropixels (0.4″ × 2.7″). Fourth row shows the maximum of the current density-magnetic field ratio (per each pixel plasma column) in three temperature bins, around the temperature peak of each line (see attached online).