How to create a line break after each 3 characters in one long line?

Question

I want to break the below line into 1000 ones by 3 letters each:

 saahaalaasabaaboabsabyaceactaddadoadsadzaffaftagaageagoagsahaahiahsaidailaimainairaisaitalaalbaleallalpalsaltamaamiampamuanaandaneaniantanyapeapoappaptarbarcarearfarkarmarsartashaskaspassateattaukavaaveavoawaaweawlawnaxeayeaysazobaabadbagbahbalbambanbapbarbasbatbaybedbeebegbelbenbesbetbeybibbidbigbinbiobisbitbizboabobbodbogboobopbosbotbowboxboybrabrobrrbubbudbugbumbunburbusbutbuybyebyscabcadcamcancapcarcatcawcayceecelcepchicigciscobcodcogcolconcoocopcorcoscotcowcoxcoycozcrucrycubcudcuecumcupcurcutcwmdabdaddagdahdakdaldamdandapdawdaydebdeedefdeldendevdewdexdeydibdiddiedifdigdimdindipdisditdocdoedogdoldomdondordosdotdowdrydubdudduedugduhduidunduodupdyeeareateauebbecuedhedseekeeleffefsefteggegoekeeldelfelkellelmelsemeemsemuendengenseoneraereergernerrersessetaetheveeweeyefabfadfagfanfarfasfatfaxfayfedfeefehfemfenferfesfetfeufewfeyfezfibfidfiefigfilfinfirfitfixfizfluflyfobfoefogfohfonfopforfoufoxfoyfrofryfubfudfugfunfurgabgadgaegaggalgamgangapgargasgatgaygedgeegelgemgengetgeyghigibgidgiegiggingipgitgnugoagobgodgoogorgosgotgoxgoygulgumgungutguvguygymgyphadhaehaghahhajhamhaohaphashathawhayhehhemhenhepherheshethewhexheyhichidhiehimhinhiphishithmmhobhodhoehoghonhophoshothowhoyhubhuehughuhhumhunhuphuthypiceichickicyidsiffifsiggilkillimpinkinninsionireirkismitsivyjabjagjamjarjawjayjeejetjeujewjibjigjinjobjoejogjotjowjoyjugjunjusjutkabkaekafkaskatkaykeakefkegkenkepkexkeykhikidkifkinkipkirkiskitkoakobkoikopkorkoskuekyelablacladlaglamlaplarlaslatlavlawlaxlaylealedleelegleileklesletleulevlexleylezliblidlielinliplislitlobloglooloplotlowloxluglumluvluxlyemacmadmaemagmanmapmarmasmatmawmaxmaymedmegmelmemmenmetmewmhomibmicmidmigmilmimmirmismixmoamobmocmodmogmolmommonmoomopmormosmotmowmudmugmummunmusmutmycnabnaenagnahnamnannapnawnaynebneenegnetnewnibnilnimnipnitnixnobnodnognohnomnoonornosnotnownthnubnunnusnutoafoakoaroatobaobeobiocaodaoddodeodsoesoffoftohmohoohsoilokaokeoldoleomsoneonoonsoohootopeopsoptoraorborcoreorsortoseoudouroutovaoweowlownoxooxypacpadpahpalpampanpapparpaspatpawpaxpaypeapecpedpeepegpehpenpepperpespetpewphiphtpiapicpiepigpinpippispitpiupixplypodpohpoipolpompoopoppotpowpoxproprypsipstpubpudpugpulpunpuppurpusputpyapyepyxqatqisquaradragrahrairajramranraprasratrawraxrayrebrecredreerefregreiremrepresretrevrexrhoriaribridrifrigrimrinriprobrocrodroeromrotrowrubruerugrumrunrutryaryesabsacsadsaesagsalsapsatsausawsaxsayseasecseesegseiselsensersetsewsexshasheshhshysibsicsimsinsipsirsissitsixskaskiskyslysobsodsolsomsonsopsossotsousowsoxsoyspaspysristysubsuesuksumsunsupsuqsyntabtadtaetagtajtamtantaotaptartastattautavtawtaxteatedteetegteltentettewthethothytictietiltintiptistittodtoetogtomtontootoptortottowtoytrytsktubtugtuituntuptuttuxtwatwotyeudoughukeuluummumpunsupoupsurburdurnurpuseutauteutsvacvanvarvasvatvauvavvawveevegvetvexviavidvievigvimvisvoevowvoxvugvumwabwadwaewagwanwapwarwaswatwawwaxwaywebwedweewenwetwhawhowhywigwinwiswitwizwoewogwokwonwoowopwoswotwowwrywudwyewynxisyagyahyakyamyapyaryawyayyeayehyenyepyesyetyewyidyinyipyobyodyokyomyonyouyowyukyumyupzagzapzaszaxzedzeezekzepzigzinzipzitzoazoozuzzzz

Please advise me on how to approach it.

Answer 1

Try the following find and replace, in regex mode:

Find:    (...)(?=.)
Replace: $1\r\n

Demo

The pattern (...)(?=.) matches and captures any three letters at a time. Then, we replace with those three letters ($1) followed by a break (I used \r\n, the Windows line ending; use \n if you are on Linux). Note that the pattern also only matches if the three letters found are not the final three letters in the string. The positive lookahead (?=.) avoids adding an unwanted break at the end.

Answer 2

This regular expression,

.{3}\K

with a replacement of:

\n

might simply do that.

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The expression is explained on the top right panel of this demo if you wish to explore/simplify/modify it.