Whether order is kept after a move must be defined

What it is

After an object moves from left to right (or back), where it lands must be a rule that can be said out loud, not a different-looking result each time. Common rules: keep the source order, append to the end of the target, re-sort alphabetically, or allow manual order in the target. Order after move matters as soon as sequence is data: export column order, display priority of grants. If the rule is mute, people shuttle items in and out trying to use moving as a sort tool, and scramble the set.

Order is a property of the target column. The source may have its own sort; they need not match, but each must be stable.

Why it happens

People read list position as importance or execution order. Landing at the right-hand end is “process last”; slipping back into a source slot is “give me my old rank.” If insertion is sometimes alphabetical and sometimes append-only, the spatial result of the same action cannot be predicted, and the handover metaphor is polluted by a sorting metaphor. Once people start moving in order to sort, add/remove is no longer a set operation but an unstable sort gesture; errors show up as wrong order rather than wrong membership — harder to notice.

If the product truly needs the target sortable, give the right column up/down or drag, and take sorting out of moving. Moving changes membership; sorting changes place.

Where it stops holding

When the set is unordered (a bag of ids, pure permission flags), still pick a stable rule (usually by name) so the surface is not random. After a user has ordered by hand, an automatic alphabetical pass destroys that labour; automatic rules should run only before a manual order exists. A move while filtered should land in the object’s place on the full roster, not at the end of the filtered view, or the place will jump when the filter clears. A source that leaves a hole after a move (not closing up following items) looks like a broken list; usually close up, unless position itself encodes some order on the unchosen set.

Applying it

• State the target order: append, follow source, by name, or manual. Put that sentence in the column’s helper text.
• When sequence is data, give the right column its own sort handles; do not make people gamble by shuttling.
• Moves during a filter land by the full-roster rule; clearing the filter must not jump the item.
• How to check: move three items in different orders, then move them back. The places must obey one rule each time; if people start shuttling “to sort a bit,” a sort entry is missing or the rule was never read.

Related

• Within the group: E3.14.1 A transfer list is for picking from a large set and seeing the selection whole · E3.14.2 Both lists need their own search and bulk actions · E3.14.4 Scan cost stays high when the set is huge
• Adjacent: E4.02 List Items
• Search terms: list order · preserve sequence · transfer sort