Configuration

Everything is at Settings → Plugins → Glue, and can be overridden in config/glue.php.

What the merge screen opens with

Setting	Default	What it does
defaultTarget	new	Where a merge writes: new, a or b. new is the default because it is the only one that cannot lose anything.
defaultStrategy	nonEmpty	How each field's choice is pre-selected: nonEmpty, a, b or combine.
defaultDisposition	leave	What happens to the originals: leave, disable or trash.

nonEmpty takes A unless A is empty and B is not. It is the default because the commonest real merge by a distance is "these two are the same entry, one of them was filled in further", and pre-selecting that turns a forty-field entry type into four decisions instead of forty.

combine pre-selects "Both" wherever the field allows it and both sides have something, and falls back to nonEmpty everywhere else.

What "Both" does

Setting	Default	What it does
textSeparator	"\n\n"	Between two plain-text values joined with "Both".
richTextSeparator	"\n"	Between two rich-text values.
dedupeRows	true	Drop a combined table row identical to one already above it.

Rich text gets a single newline rather than a blank line because it already carries its own block spacing: </p>\n\n<p> renders exactly like </p>\n<p>, so the extra newline is visible only in the diff.

An empty separator is allowed and means straight concatenation. It is almost never what you want for prose — check the Result column before you rely on it.

Rewiring — Pro

Setting	Default	What it does
rewireRelations	false	Whether the rewire switch starts on.
rewireThreshold	25	Above this many referencing elements, rewiring goes to the queue. 0 never queues.

Off by default even on Pro. Rewiring edits other people's entries, and a setting that quietly does that on somebody's first merge is a setting that gets the plugin uninstalled. Turn it on once you have watched it work.

Rewiring only saves elements the merging user could have saved themselves, in sites they can edit. Anything else is skipped and counted in the result, so a merge is never a way to change pages the user has no access to. The console is not limited this way.

The threshold exists because each rewire is a full element save — content, relations, search index, revision. A few dozen is a slow response; a few thousand is a timed-out one.

Multi-site — Pro

Setting	Default	What it does
allSites	false	Whether "merge in every site" starts on.

History

Setting	Default	What it does
logMerges	true	Record every merge in glue_merges.
historyLimit	500	Merges to keep. Older rows are pruned during garbage collection. 0 keeps everything.

Pruning happens in garbage collection rather than on write, so an afternoon of merging does not pay for a DELETE per merge. Being a hundred rows over the limit between two nightly runs costs nothing.

Presets — Pro

presets is a map of saved plans, keyed by handle. It is written by the Save as preset button on the merge screen; there is rarely a reason to write one by hand, but it is readable:

'presets' => [
    'press-release-dedupe' => [
        'name' => 'Press release dedupe',
        'entryTypeId' => 12,
        'target' => 'a',
        'choices' => [
            'body' => 'combine',
            'topics' => 'combine',
            'heroImage' => 'a',
            'legacyId' => 'blank',
        ],
        'titleFrom' => 'a',
        'slugFrom' => 'a',
        'authorFrom' => 'a',
        'postDateFrom' => 'earliest',
        'statusFrom' => 'a',
        'parentFrom' => 'a',
        'disposition' => 'trash',
        'rewire' => true,
        'allSites' => false,
    ],
],

A handle absent from choices is not the same as one set to blank: absent means "no opinion" and falls back to the pre-selection rule, which is what lets a preset be replayed against an entry type it was not written for.

A config file

<?php
// config/glue.php

return [
    '*' => [
        'defaultStrategy' => 'nonEmpty',
        'defaultDisposition' => 'leave',
        'textSeparator' => "\n\n",
        'logMerges' => true,
    ],
    'production' => [
        // Rewiring on production, where the inbound links actually matter.
        'rewireRelations' => true,
        'rewireThreshold' => 10,
    ],
];

Settings in config/glue.php are read-only in the control panel, as with any Craft plugin.