\useMPlibrary[dum]

\starttext

First line.

\startplacefigure[location=here,reference=first,title=first]
    \externalfigure[dummy][height=2cm]
\stopplacefigure

Second line.

\startplacefigure[location=here,reference=second,title=second,group=alpha,groupsuffix=.a]
    \externalfigure[dummy][height=2cm]
\stopplacefigure

Third line.

\startplacefigure[location=here,reference=third,title=third]
    \externalfigure[dummy][height=2cm]
\stopplacefigure

Fourth line.

\startplacefigure[location=here,reference=fourth,title=fourth,group=alpha,groupsuffix=.b]
    \externalfigure[dummy][height=2cm]
\stopplacefigure

Fifth line.

\startplacefigure[location=here,reference=fifth,title=fifth,group=alpha,groupsuffix=.c]
    \externalfigure[dummy][height=2cm]
\stopplacefigure


Last line: \in[first] / \in[second] / \in[third] / \in[fourth] / \in[fifth].

\page

\placelist[figure]

\stoptext


\startplacefigure[location=here,reference=first, title=first, group=alpha,groupsuffix=.a]
    \externalfigure[dummy][height=2cm]
\stopplacefigure
\startplacefigure[location=here,reference=second,title=second,group=alpha,groupsuffix=.b]
    \externalfigure[dummy][height=2cm]
\stopplacefigure


\stoptext
