Pelargonium alchemilloides leaves are mainly recognised by two characteristics: the purple ring or zone around the leaf centre and the deep incisions forming narrow lobes with tips toothed and lateral margins entire (not occurring in the plant in picture).
As shown, neither feature is always present in this variable species, like only the ring being present in this photo and no incisions. The leaf incisions of markedly lobed leaves shown in other photos of this Album occur with and without the coloured, central ring or zone.
Both these features are also shared with other Pelargonium species, such as the rings appearing for instance on P. zonale leaves and the smooth incisions on P. gibbosum leaves.
Identification is based on more though: The overall configuration of each set of specific characteristics allows for a plant to be identified in spite of key or dominant features being shared, even widely.
The embedded subtleties yielding an identification are then picked up via pattern recognition, largely subconsciously. What is added is the familiarisation of repetition, over time functioning like intuition.
In this way the shepherd may know his sheep individually in a big flock, deemed a hard skill to master, and the mother her children, deemed easy, for there are fewer children and more repetitions of contact per child (Vlok, 2015; Manning, 2009; iNaturalist).