The article discusses how micro-level textual variation can be expressed in an idiomatic manner using markup, and how the markup information is subsequently used by a digital collation tool for a more refined analysis of the textual variation. We take as a case study the manuscript materials of Virginia Woolf's To the Lighthouse (1927) that bear the traces of the author's struggles in the form of deletions, additions, and rewrites. These in-text revisions typically constitute non-linear, discontinuous, or multi-hierarchical information structures. While digital technology has been instrumental in supporting manuscript research, the current data models for text provide only limited support for co-existing hierarchies or non-linear text features. The hypergraph data model of TAG is specifically designed to support and facilitate the study of complex manuscript text by way of its syntax TAGML and the collation tool HyperCollate. The article demonstrates how the study of textual variation can be augmented by computer-assisted collation that takes into account in-text, micro-level revisions.