The fabrication of novel steel grades with appealing mechanical properties and printability is necessary for additive manufacturing (AM). Strength, ductility, and toughness are desirable mechanical properties, and crack/pore formation prevention can be used to increase printability. In order to fabricate marageing steels with less sensitivity to solidification cracking and to achieve desirable fully martensitic microstructures upon laser powder bed fusion AM, a computational method is suggested. The model is based on an alloy design approach that combines thermodynamic calculations with a genetic algorithm to find novel marageing steel compositions; the new alloys are printed successfully crack-free while exhibiting improved strength. Crack prevention is achieved by managing the solidification temperature range (STR) and optimising the ratio between the yield strength and the coefficient of thermal expansion of the alloy at high temperatures, known as performance index (PI). The solidification path, which can be controlled via the ratio between chromium and nickel equivalents ($Cr_{eq}$ and $Ni_{eq}$), the temperature at which the remaining $\delta$-ferrite transforms fully to austenite ($A_{s}$ temperature) , and the temperature at which martensite starts to form upon quenching ($M_{s}$ temperature) control the desirable microstructures in the alloy design scheme. In order to maximise precipitation hardening in such marageing steels, composition-related criteria to optimise ageing treatment are applied.