this is the closest to searching within your favorite observations as i think you can get: https://www.inaturalist.org/observations?id=131399422,132036727,132132736,10510962,129836462,131664774,85717738,126642875,127396647,126416991,125553414,31765447,86185265,80779678,18294720,118246843,111958921,111350509,55910999,110055462,20735904,102525890,106191902,65316673,82682294,79702664,104604399,41693777,59627332,79944958,102989600,80265366,80365018,99947449,80470988,90736857,95662803,4989866,81121152,88046126,89973268,93367500,93416765,81345755,88504979,81687280,81694984,83401597,88570430,82277144,87209014,51604152,52046131,51627651,82264624,81695171,81920330,82233189,82237493,82354119,84055074,84697335,83940759,82096494,83867387,82894372,83848982,83058595,83060621,82948482,82430007,80803516,81331713,81461477,81388125,82042808,82043048,82061311,1536615,82039992,81567351,81577243,81229937,80519818,80792637,73492798,80277520,80399419,80430064,80432585,80446256,80445704,80437231,80441978,80313979,80317481,80321331,80268738,80194843,78989621,80143457,80051880,80026168,79434080,79459466,79443232,79338634,79380587,79322716,79226426,79190065,79043236,79101198,79008377,78921914,78703114,78588142,78657123,78427686,78536679,78507468,77636859,78249361,78149223,20217747,20916541,77562022,3810193,34206057,75954039,76355230,76213163,76333440,7561228,75031689,74960236,1724790,74778041,6250484,72282781,71417921,71155217,70409096,69791498,69768992,69222778,14188735,37991725,66862063,66401863,62379715,61595702,61502255,61450949,18221005,60517666,60444488,15617528,59370289,57825167,58252826,58113309,58131259,32321203,54766643,51350682,49053713,41685361,49278373,46296229,45675054,26771144,43130715,42156001,41803625,41592036,41455639,21785571,40853176,40516282,17874369,38423749,36923332,34594988&taxon_id=83854.
more info here and the rest of the thread: https://forum.inaturalist.org/t/add-search-feature-in-favorites/2502/19.